EF1 Tornado — Lassen, California

2020-08-15 · near Coyoteville, Lassen, California

Event narrative

A mesoanticyclone embedded within a deep pyrocumulonimbus updraft inside the Loyalton wildfire perimeter generated an EF1 rated anticyclonic tornado that snapped several quaking aspen trees (DI 27, DOD 4) along a 0.09-mile path on the northeast facing slope of Roberts Canyon. The tornado spun up 0.37 miles south-southwest of the intersection of Forest Service Road 182 and Forest Service Road 31182 and dissipated 0.46 miles south-southwest of the aforementioned intersection. The damage path had a maximum width of 20 yards. No injuries or deaths occurred with this tornado.

Wider weather episode

Dry conditions and anomalously low fuel moisture, in combination with an unstable low-to-mid-level atmosphere, allowed the Loyalton wildfire to develop extreme fire behavior on the afternoon of 15 August 2020. Robust heat and moisture fluxes from the wildfire caused rapid smoke plume deepening and lofting of pyrometeors above the lifting condensation level, which led to the formation of two vertically extensive pyrocumulonimbi and three tornadoes.

View location on OpenStreetMap → (39.7239, -120.1303)

Source: NOAA Storm Events Database, event_id 916709. Narrative written by the NWS forecast office that issued the report.